Leishmania major infections in Phlebotomus duboscqi fed on murine models immunized with L. major subcellular antigens and sandfly gut antigens.

The ability of antibodies in bloodmeals of mice and hamsters immunized with Leishmania major subcellular fractions and sandfly (Phlebotomus duboscqi) gut antigens to inhibit development of L. major in its vector P. duboscqi was examined. Antibodies from animals immunized with either L. major subcellular fractions alone or sandfly gut antigen alone were not very effective in inhibiting development of L. major in the sandfly. When P. duboscqi were fed on blood from animals immunized with both parasite flagella and sandfly gut antigen, development of L. major was significantly inhibited (P<0,05). Control sandflies fed on naive animals displayed a normal pattern of parasite development to the metacyclic stage. Electron microscopy studies showed that one of the mechanisms through which antisandfly gut antibody can cause inhibition of parasite development is by lysing sandfly gut epithelium. This study has demonstrated that it is possible to reduce transmission of leishmaniosis through immunization against both the parasite and its sandfly vector.

Epidemiological study of the G serotype distribution of group A rotaviruses in Kenya from 1991 to 1994.

An epidemiological study on the G serotype distribution of group A rotaviruses (GARV) isolated in Kenya was carried out in one urban hospital in Nairobi and in two rural hospitals in Nanyuki and Kitui to clarify the prevalent G serotypes before future introduction of the ready licensed rotavirus vaccine in Kenya. A total of 1,431 stool specimens were collected from children, who were mainly outpatients, aged from 0 to 6 years old with acute gastroenteritis from August 1991 to July 1994. Samples positive for GARV by conventional ELISA were then analyzed by subgrouping and serotyping ELISA and by PAGE. To ascertain the G serotypes of viruses in samples that were unable to be typed by serotyping ELISA, polymerase chain reaction was also attempted. The prevalence of GARV was 28.4% in the urban hospital, 22.5% in Nanyuki, and 13.7% in Kitui. Among rotavirus-positive samples, subgroup II rotaviruses were detected in 63.1%, and subgroup I rotaviruses were 25.9%. Serotype G4 was most prevalent, accounting for 41.6% followed by 23.3% of serotype G1, 17.0% of serotype G2, and serotype G3 was rarely isolated. Seven strains of serotype G8/P1B rotavirus was detected for the first time in Kenya by RT-PCR. Eleven specimens with an unusual composition of subgroup, serotype, and electropherotype were atypical GARV in which the P-serotype was P1A, P1B, or P2. Although uncommon GARV serotype G8/P1B and atypical GARV were detected, the four major GARV serotypes, G1 through G4, should be targeted at this moment for vaccination to control this diarrheal disease in Kenya. Continuous monitoring of the G- and P-serotype distribution of GARV should provide important information about the impact of rotavirus vaccination in Kenya.

The effects of a tsetse DNA virus infection on the functions of the male accessory reproductive gland in the host fly Glossina morsitans centralis (Diptera; Glossinidae).

Freshly deposited third instar Glossina morsitans centralis larvae were infected with the tsetse DNA virus by microinjection, and at emergence adult males were separated from the females and fed on rabbit blood every second day for 8 days. A control group treated with sterile saline were handled similarly. They were dissected, and comparative observations made on the appearance and size of the accessory reproductive glands (ARG) in infected and control males. Regularly fed 8-day-old males from infected and control groups were mated to 2-day-old normal females obtained from the insectay. After separation from copula, the females were dissected and the uteri examined for the presence and quality of the spermatophore. The spermathecae were also examined for insemination. ARG tissues from the control and virus infected regularly fed 8-day-old male flies were fixed and processed for electron microscopic studies. The ARGs from control flies were found to be milky in appearance, whereas those from virus-infected flies were transparent in most parts. The ARGs from virus-infected males were significantly smaller in diameters (F = 42.26, p < 0.0001) and shorter (F = 200.4, p < 0. 0001) than those of the controls. Most of the virus-infected males failed to form a complete spermatophore, whereas almost all the controls formed complete spermatophore as observed in the uteri of the female mates (Chi2 = 111.661, p < 0.0001). The infected males that formed partial spermatophores and those that did not form any at all failed to inseminate their female mates. Histological studies of the ARGs revealed some lesions in the epithelial cells characterized by degeneration of cytoplasmic organelles and detachment of the muscle layer from the basal plasma membrane. However, no virus particles were observed in the affected cells.

Ultrastructural Changes in the Milk Gland of Tsetse Glossina morsitans centralis (Diptera; Glissinidae) Female Infected by a DNA Virus

Milk glands, dissected out and collected from Glossina morsitans centralis (Machado) females, artificially inoculated at the third-instar larval stage with a virus suspension obtained from hypertrophied salivary glands of wild-caught virus-infected Glossina pallidipes (Austen), were processed for routine electron microscopy and examined for pathological changes. They were compared to milk glands dissected out from normal female G.m. centralis at the same stage of pregnancy cycle. Upon dissection there were notable physical differences between control and virus-infected milk glands. Histologically, some areas of the gland developed severe degeneration while other areas developed less severe pathological changes. Ultrastructural studies revealed the presence of virus particles in the secretory cell nuclei and within the cytoplasm and also showed that the nucleus was the site of virogenesis with mature naked virions budding through the nuclear membrane and acquiring the envelope from the nuclear membrane. Milk glands from normal females showed normal cellular organization of the secretory cells and secretory vesicles around the collecting gland lumen. The demonstration of virus particles in the secretory cell nuclei and cytoplasm suggests another mode of transmission of the virus from the infected mother to the larva in utero.

Characterization of human rotavirus strains causing gastroenteritis in Kenya.

Human rotavirus strains from Kenya, from children with gastroenteritis in an urban area (Nairobi) and three rural areas were characterized by antigenic and genomic analysis. While in all areas strains with subgroups II and G serotype 1 antigens were most common, two unusual strains were detected. One strain (NK59: subgroup II, G serotype 4) possessed an additional RNA band on polyacrylamide gel electrophoresis, the other (D202) which had antigenic specificity of subgroup II and G serotype 1 showed a 'short' RNA pattern. The latter strain was adapted to growth in cell culture.

The outcome of a pilot study on the epidemiology of rotavirus in three District Hospitals in Kenya-March 1990

This pilot study was done in preparation to assist in chosing the appropriat site for a 5-year main study. The study aim was to find the differences in epidemiology of rotavirus (RV) and other viral agents causing gastroenteritits in children in Kenya between an urban hospital; in this case Kenyatta National Hospital; and a rural hospital to be chosen from Narok; Nanyuki or Kitui district hospitals. Stool specimens were collected for two weeks during the same period from children aged 0 to 14 years attending outpatient clinics and those admitted with diarrhoea at the hospitals. Stool specimens were subsequently analysed by the ELISA method. The presence of RV was confirmed by the sodium dodecyl sulphate polyacrylamide gel electrophoresis method which demonstrates the electrophoretic pattern of the RNA genome. The RV positive rates were 35 (21 in 60) in Nanyuki; 13.8 (4 in 29) in Narok and 1.8 (1 in 56) in Kitui. From these 26 RV strains; 8 (7 long and one short) electropherotype patterns were demonstrated. Subgrupingand serotyping was also done by ELISA method on the 26 isolates yielding 2 subgroup I and 24 subgroup II. The major serotypes were 1(30.8) and 4(26.9) while serotypes were undeterminable in 10 positive specimens. Tissue culture using MA104 cells yielded 5 strains from these positive specimens